A-M baby

Task/Modular-inverse/D/modular-inverse.d

@@ -0,0 +1,23 @@
+T modInverse(T)(T a, T b) pure nothrow {
+    if (b == 1)
+        return 1;
+    T b0 = b,
+      x0 = 0,
+      x1 = 1;
+
+    while (a > 1) {
+        immutable q = a / b;
+        auto t = b;
+        b = a % b;
+        a = t;
+        t = x0;
+        x0 = x1 - q * x0;
+        x1 = t;
+    }
+    return (x1 < 0) ? (x1 + b0) : x1;
+}
+
+void main() {
+    import std.stdio;
+    writeln(modInverse(42, 2017));
+}